《TOFD检测（双语）》课件-19.时间窗口设置

时间窗口设置

TimewindowsettingTOFD检测技术

TOFDTestingTechnologyTOFD检测设置时间窗口设置原则

PrinciplesforSettingtheTimeWindowinTOFDTesting1整体一次扫查时间窗口设置

Time-WindowSettingforaSingleFull-ThicknessScan2深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth3知识目标

Knowledgeobjectives教学目标

TeachingobjectivesTOFD检测设置时间窗口分两种情况

ThetimewindowforTOFDtestingissetdifferentlyforthefollowingtwoscanningconditions整体一次扫查：以直通波、波型转换底波为依据，窗口的起始位置应设置在直通波到达接收探头前，窗口宽度应设置在工件底面的一次波型转换波后，以便观察底面反射纵波信号之后是否有信号显示。

Singlefull-thicknessscan:Thetimewindowissetwithreferencetothelateralwaveandthemode-convertedback-wallsignal.Thestartofthewindowshouldbepositionedbeforethelateralwavereachesthereceivingprobe,andtheendshouldbepositionedafterthefirstmode-convertedback-wallsignalsothatanysignalsoccurringafterthelongitudinal-waveback-wallechocanbeobserved.TOFD检测设置时间窗口设置原则

PrinciplesforSettingtheTimeWindowinTOFDTesting有些近表面缺陷，其纵波信号出现在直通波附近，因而难以观察到。

Thelongitudinal-wavesignalsfromsomenear-surfacedefectsoccurclosetothelateralwaveandarethereforedifficulttoobserve.但这些缺陷同时会产生以横波形式传播的信号，因为横波声速大约是纵波的一半，而这些信号出现在底面反射纵波信号之后，观察这些信号对发现和验证某些缺陷是有用处的。

However,thesedefectsmayalsogeneratesignalsthatpropagateasshearwaves.Becausetheshear-wavevelocityisapproximatelyhalfthelongitudinal-wavevelocity,thesesignalsoccurafterthelongitudinal-waveback-wallecho.Observingthemcanassistindetectingandverifyingcertaindefects.TOFD检测设置时间窗口设置原则

PrinciplesforSettingtheTimeWindowinTOFDTestingTOFD检测设置时间窗口分两种情况

ThetimewindowforTOFDtestingissetdifferentlyforthefollowingtwoscanningconditions深度分区扫查：有些分区没有直通波和底波，对这些扫查区就必须通过计算设置时间窗口，并在对比试块上校核。

Zonalscanningbydepth:Someinspectionzonescontainneitheralateralwavenoraback-wallecho.Forthesezones,thetimewindowmustbedeterminedbycalculationandverifiedonareferenceblock.TOFD检测设置时间窗口设置原则

PrinciplesforSettingtheTimeWindowinTOFDTestingTOFD检测设置时间窗口分两种情况

ThetimewindowforTOFDtestingissetdifferentlyforthefollowingtwoscanningconditions校核时应保证每一个区的时间窗口在深度方向覆盖相邻分区。

Duringverification,thetimewindowforeachzoneshouldprovideoverlappingdepthcoveragewiththeadjacentzones.深度分区一般依据NB/T47013.10《承压设备无损检测第10部分：衍射时差法超声检测》，厚度方向分区扫查时间窗口设置。

Zonalscanningbydepthanditstime-windowsettingsaregenerallydeterminedinaccordancewithNB/T47013.10,Non-DestructiveTestingofPressureEquipment—Part10:UltrasonicTime-of-FlightDiffractionTechnique.TOFD检测设置时间窗口设置原则

PrinciplesforSettingtheTimeWindowinTOFDTestingTOFD检测设置时间窗口分两种情况

ThetimewindowforTOFDtestingissetdifferentlyforthefollowingtwoscanningconditions适用：工件厚度≤50mm、单通道。

Application:Single-channelinspectionofworkpieceswithathicknessof50mmorless.标准规定：

StandardRequirements起始：直通波到达前≥0.5μs；

Startposition:Atleast0.5μsbeforethearrivalofthelateralwave;终止：底面一次波形转换波后≥0.5μs；

Endposition:Atleast0.5μsafterthefirstmode-convertedback-wallsignal;将直通波与工件底面反射波时间间隔所反映的厚度校准为已知的工件厚度。

Calibratethedepthscalesothatthethicknessindicatedbythetimeintervalbetweenthelateralwaveandtheback-wallechomatchestheknownworkpiecethickness.整体一次扫查设置时间窗口

Time-WindowSettingforaSingleFull-ThicknessScan没有直通波

NoLateralWave整体一次扫查设置时间窗口

Time-WindowSettingforaSingleFull-ThicknessScan时间窗口太大

TimeWindowTooWide整体一次扫查设置时间窗口

Time-WindowSettingforaSingleFull-ThicknessScan适用范围

ScopeofApplication厚度＞50mm、多通道分区，完全执行NB/T47013.10。

Thismethodappliestomultichannelzonalinspectionofworkpieceswithathicknessgreaterthan50mmandshouldbeimplementedinaccordancewithNB/T47013.10.总体要求：

GeneralRequirements:用对比试块设窗口、做深度校准；

Useareferenceblocktosetthetimewindowandcalibratethedepthscale;窗口至少覆盖所需深度范围；

Thetimewindowmustcoveratleasttherequireddepthrange;分区之间必须重叠覆盖，不留盲区。

Adjacentzonesmustoverlapsothatnouninspectedregionremains.最下分区的时间窗口终止位置应设置为底面反射波到达接收探头后0.5μs以上。

Theendofthetimewindowforthelowestzoneshouldbepositionedatleast0.5μsaftertheback-wallechoreachesthereceivingprobe.深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth无直通波、无底线分区：计算设窗口、试块校核；

Zoneswithoutalateralwaveorback-wallecho:Determinethetimewindowbycalculationandverifyitonareferenceblock;最上分区：起始直通波前≥0.5μs，终止本区最大深度；

Uppermostzone:Setthestartpositionatleast0.5μsbeforethelateralwaveandtheendpositionatthemaximumdepthofthezone;深度分区扫查——标准5条要点

ZonalScanningbyDepth:FiveKeyRequirementsoftheStandard深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth中间分区：向上覆盖上一分区25%厚度（标准强制）；

Intermediatezones:Extendthetimewindowupwardtocover25%ofthethicknessoftheprecedingzone,asmandatorilyrequiredbythestandard;最下分区：终止底波后≥0.5μs；

Lowestzone:Settheendpositionatleast0.5μsaftertheback-wallecho;所有分区：深度方向互相覆盖，全厚度无盲区。

Allzones:Provideoverlappingcoverageinthethrough-thicknessdirectionsothattheentirethicknessisinspectedwithoutanygaps.深度分区扫查——标准5条要点

ZonalScanningbyDepth:FiveKeyRequirementsoftheStandard深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth厚度T=56mm工件为例来计算时间窗口的设置，5MHz，60°楔块。

Thefollowingexampleillustratesthecalculationoftime-windowsettingsforaworkpiecewithathicknessTof56mmusing5MHzprobeswitharefractedangleof60°.深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth将第一通道聚焦于工件2t/5的2/3处，利用三角函数计算

PositionthebeamintersectionpointforChannel1attwo-thirdsofthefirstzone,whichextendsfrom0to2T/5,andcalculatethePCSusingtrigonometricrelationships利用三角函数对第二通道PCS计算

CalculatethePCSforChannel2usingtrigonometricrelationships深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth计算第一通道直通波时间：52/5.9=8.81μs因为直通波前要求有0.5μs，所以在仪器上将第一通道显示延迟设置为8.81-0.5=8.3μs，

Thelateral-wavetransittimeforChannel1is52/5.9=8.81μs.Becausethetimewindowmuststartatleast0.5μsbeforethelateralwave,setthedisplaydelayforChannel1to8.81−0.5=8.31μs,根据三角函数计算第一通道2t/5处声束传播时间为：

Theultrasonictransittimeatadepthof2T/5forChannel1iscalculatedusingtrigonometricrelationshipsasfollows:深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth第二通道因为要求向上覆盖2t/5的25%，依据三角函数计算时间窗口的起始位置计算为：

BecauseChannel2mustextendupwardtocover25%ofthefirstzone,whichextendstoadepthof2T/5,thestartpositionofitstimewindowiscalculatedusingtrigonometricrelationshipsasfollows:依据三角函数计算底波时间窗口的终止位置为：

Thearrivaltimeoftheback-wallecho,whichdeterminestheendpositionofthetimewindow,iscalculatedusingtrigonometricrelationshipsasfollows:因为要求底波后有0.5μs，因此应将声程设置为32.41+0.5=32.91μs

Becausethetimewindowmustextendatleast0.5μsbeyondtheback-wallecho,itsendpositionshouldbesetto32.41+0.5=32.91μs.深度分区扫查时间窗口设置

Time-WindowSettingforZonalScanningbyDepth01TOFD时间窗口：是仪器采集超声波信号的时间范围，目的是完整采集工件有效厚度范围内的直通波、缺陷衍射波和底面回波，同时屏蔽无用信号。

ATOFDtimewindowisthetimerangeoverwhichtheinstrumentacquiresultrasonicsignals.Itissettocapturethelateralwave,defect-diffractedsignals,andback-wallechothroughouttheeffectivethicknessrangeoftheworkpiecewhileexcludingirrelevantsignals.02时间窗口的起始位置：一般设置在直通波前方，保证完整收录直通波信号；窗口结束位置设置在底面回波之后，确保全厚度范围信号不丢失。

Thestartofthetimewindowisgenerallypositionedbeforethelateralwavetoensurethatthecompletelateral-wavesignalisrecorded.Theendispositionedaftertheback-wallechotoensurethatnosignalsfromthefullthicknessrangearelost.小结Summary03时间窗口设置原则：窗口不能过小，否则会切掉近表面、底面缺陷信号，造成漏检；窗口不能过大，否则会采集多余杂波，降低图像清晰度、影响分辨力。

Thetimewindowmustnotbetoonarrow,asthismayexcludesignalsfromdefectsnearthein